The present application generally relates to a gas lift barrier and associated side pocket mandrel design. For purposes of communicating well fluid to a surface of a well, a well may include production tubing. More specifically, the production tubing typically extends down hole into a wellbore of the well for purposes of communicating well fluid from one or more subterranean formations through a central passageway of the production tubing to the well's surface. Due to its weight, the column of well fluid that is present in the production tubing may suppress the rate at which the well fluid is produced from the formation. More specifically, the column of well fluid inside the production tubing exerts a hydrostatic pressure that increases with well depth. Thus, near a particular producing formation, the hydrostatic pressure may be significant enough to substantially slow down the rate at which the well fluid is produced from the formation.
For purposes of reducing the hydrostatic pressure and thus, enhancing the rate at which fluid is produced, an artificial-lift technique may be employed. One such technique involves injecting gas into the production tubing to displace some of the well fluid in the tubing with lighter gas. The displacement of the well fluid with the lighter gas reduces the hydrostatic pressure inside the production tubing and allows reservoir fluids to enter the wellbore at a higher flow rate. The gas to be injected into the production tubing typically is conveyed down hole via the annulus (the annular space surrounding the production tubing) and enters the production tubing through one or more gas lift barrier valves.
A gas lift system can include production tubing that extends into a wellbore. For purposes of gas injection, the system includes a gas compressor that is located at the surface of the well to pressurize gas that is communicated to an annulus of the well. To control the communication of gas between the annulus and a central passageway of the production tubing, the system may include several side pocket gas lift mandrels. Each of the gas lift mandrels can have an associated gas lift barrier valve for purposes of establishing one way fluid communication from the annulus to the central passageway. Near the surface of the well, one or more of the gas lift barriers may be unloading valves. An unloading gas lift barrier opens when the annulus pressure exceeds the production tubing pressure by a certain threshold, a feature that aids in pressurizing the annulus below the valve before the valve opens. Other gas lift barriers, typically located farther below the surface of the well, may not having an opening pressure threshold.
The gas lift barrier can contain a one way check valve element that opens to allow fluid flow from the annulus into the production tubing and closes when the fluid would otherwise flow in the opposite direction. For example, the production tubing may be pressurized for purposes of setting a packer, actuating a tool, performing a pressure test, etc. Thus, when the pressure in the production tubing exceeds the annulus pressure, the valve element is closed to ideally form a seal to prevent any flow from the tubing to the annulus. However, it is possible that this seal may leak, and if leakage does occur, well operations that rely on production tubing pressure may not be able to be completed or performed. Thus, an intervention may be needed, which may be costly, especially for a subsea well.
Thus, there exists a continuing need for better ways to increase reliability of gas lift barrier valves and to prevent a gas lift barrier assembly/design from leaking.